Improve dry run output

[Gudahtt]

The npm dry run publish step currently lists the files that will appear in the package, but it could be much more informative for reviewers.

e.g. something like this:

These files changed:
[ list of files with size changes]

These files were deleted:
[ list of files with sizes]

These files were added:
[ list of files with sizes]

[rickycodes]

I'm going to create a new issue for the "Bundle size diff" functionality that was previously mentioned here.